8013

• UCREFRP Catalog Number: 8013
• Author: Pontius, D. and I. SWCA.
• Title: Colorado River Basin Study.
• USFW Year: 1997.
• USFW - Doc Type: Tucson, Arizona.
• Copyright Material: NO

Colorado River Basin Study

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because the Colorado River Compact, which allocated the river's water, was
negotiated in 1922. Since 1922, estimates of the river's average flow have
been consistently revised downward.

Water Development

While most river basins in North America have less than two times the
annual water supply in reservoir storage, reservoirs on the Colorado River
have a total live capacity more than four times the average annual flow. As
shown in Table 1, the total live storage capacity of major reservoirs in the
basin is more than 60 maf. The capacity of the two principal reservoirs,
Lake Mead and Lake Powell, is greater than 50 maf.

The unusually large storage capacity has diminished impacts of drought
within the basin, at least in the short term. Growing demands on the river,
however, may reduce the ability of these reservoirs to provide a buffer
against drought. Most of the reservoir storage is located too far downstream
for direct use ill the Upper Basin, and most of the water in storage in the
Upper Basin is used to satisfy Compact guarantees to the Lower Basin and
for Mexico's entitlement.

Evaporative losses from the Colorado River reservoirs are especially high due
to the arid climate of the region. As shown in Table 2, the average annual
evaporative loss from reservoirs in the basin is more than 2.0 maf. It has
been reported that the optimum level of storage in the basin, beyond which
there is no net increase in usable supply due to evaporative losses, has been
surpassed (Langbein, 1959; Hardison, 1972).

Diversions

Colorado River water is diverted for use both in and out of the basin at
hundreds of diversion points. There are considerably more diversions in the
Upper Basin, but Lower Basin diversions are much larger. Representative
water development projects in the Upper Basin are shown in Figure 4. On
an annual basis, more than a third of the river's supply is exported from the
basin, including diversions to such cities as Denver, Colorado Springs, Salt
Lake City, Albuquerque, Los Angeles, and San Diego. These service areas, in
combination with the actual Colorado River basin, have been referred to as

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